Variation and Natural Selection

Question 1

What is a species?

Answer 1

• Organisms that are similar
• Able to breed and produce fertile and offspring

Question 2

What are humans?

Answer 2

species

Question 3

What is variation?

Answer 3

Differences in the characteristics within a species

Question 4

Variation is caused by:

Answer 4

• Genes
• Environment
• A combination of both

Question 5

Jane and Hannah are friends. Jane is taller than Hannah and has pierced ears. Hannah does not have any piercings. Jane has brown eyes, whilst Hannah has green eyes.

Identify examples of variation between Jane and Hannah caused by genes, the environment or a combination of both.

1. Variation caused by genes:
2. Variations caused by the environment:
3. Variation caused by a combination of genes and the environment:

Answer 5

1. Eye color
2. Piercings
3. Height

Question 6

A person’s tattoos

Answer 6

Environmental

Question 7

The height a sunflower grows
to

Answer 7

A combination of both

Question 8

The stripes on a tiger

Answer 8

Genetic

Question 9

The mass of an elephant

Answer 9

A combination of both

Question 10

A person’s eye colour

Answer 10

Genetic

Question 11

A person’s accent

Answer 11

Environmental

Question 12

What is genetic variation caused by

Answer 12

Mutations to genes

Question 13

A mutation is a change…

Answer 13

to the genetic code of an
organism.

Question 14

Mutations happen randomly…

Answer 14

and continuously when DNA is
copied.

Question 15

Most mutations have…

Answer 15

no effect on an organism’s
phenotype.

Question 16

What is the first stage of
natural selection?

Answer 16

Variation caused by mutations

Question 17

What is the second stage
of natural selection?

Answer 17

Competition for a resource

Question 18

What is the third stage of
natural selection?

Answer 18

An individual of the species has
a survival advantage

Question 19

What is the final stage of
natural selection?

Answer 19

Survivors breed and pass their
genes onto offspring

Question 20

What variation is there? What
caused this? (Giraffes)

Answer 20

A mutation has caused variation in giraffe
neck length

Question 21

What competition is there? (Giraffes)

Answer 21

There is competition for food

Question 22

Who has the survival advantage
and why? (Giraffes)

Answer 22

• Giraffes with longer necks have the
  survival advantage
• As they can reach food higher up in trees

Question 23

What are survivors able to do? (Giraffes)

Answer 23

Survivors breed and pass on the gene for long necks to offspring

Question 24

Genetic changes can contribute to the process of natural selection.

Explain how.

Answer 24

• Passes the gene and
• Characteristic/genetic
• Change/mutation (onto its offspring)

Question 25

Hedgehogs are covered in small spines.

When they are frightened they often roll up into a ball and keep still.

In country areas, where badgers live, this is an advantage to the hedgehogs.

In cities, where there are many roads, this is a disadvantage.

Explain these two conclusions

Answer 25

• in cities is a disadvantage
• Many roads, will be run over by cars
• In the country is an advantage
• Badgers live, if it rolls up in a ball then it will provide more protection

Question 26

Scientists have noticed that a new type of hedgehog is increasing in numbers in cities.

These hedgehogs do not roll up. They run away when frightened. The scientists think
that genes control this behaviour.

Explain how this type of hedgehog may become more common in cities.

Use ideas about natural selection.

Answer 26

• Hedgehogs that run away are more likely to survive
• Less likely to get run over
• They will reproduce ✓
• Pass on the allele/gene for running away ✓
• Overtime/many generations (running away will become more common)